Propofol formulated with long-/medium-chain triglycerides reduces the pain of injection by target controlled infusion

Background: Propofol is a widely used intravenous anesthetic although its injection pain is a common and unpleasant problem. Long-/medium-chain triglyceride (LCT/MCT) propofol has been introduced, as its low free propofol content is expected to reduce injection pain compared with LCT propofol. Target controlled infusion (TCI) differs from conventional induction in the initial infusion pattern. During induction using TCI, we investigated injection pain caused by two propofol solutions with different triglyceride compositions. Methods: Fifty patients, ASA I–II, with adequate communicative ability, were randomly assigned to two groups. TCI was conducted with Diprifusor for LCT and with BeComSim (custom-made software) for LCT/MCT. The target blood concentration was set at 4 μg/ml for both groups. At 30, 60, and 120 s after the infusion, patients were asked questions regarding the severity of pain on a 0–10 pain score. The total dose of propofol and the time required to induce anesthesia were also investigated. Results: The LCT/MCT propofol group had a larger number of pain-free patients and showed lower severity of pain than the LCT group [the number of pain-free patients being 11 and 3, respectively (P